Dyeing of polypropylene



"United States Patent 3,507,605 DYEING OF POLYPROPYLENE Walter H. Hindle, New York, N.Y., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Jan. 27, 1966, Ser. No. 523,251 Int. Cl. C09b 9/00, 49/00 US. Cl. 8-34 7 Claims ABSTRACT OF THE DISCLOSURE Polypropylenes containing bis-amides, bis-urethanes, and aliphatic amine modifiers are vat dyed in a dye bath containing polyvinyl-pyrrolidone.

This invention relates to vat dyeing of certain modified polypropylene materials. In one aspect, it relates to a process of vat dyeing modified polypropylene by incorporating in the dye bath polyvinylpyrrolidone. In another aspect, it relates to a modified polypropylene dyed product formed by dyeing polypropylene in a dye bath containing polyvinylpyrrolidone.

Because of its exceptional properties in fabric applications, polypropylene has become widely used in various textile forms, as for example in the production of carpets. A persistent problem, however, in production of such textile materials has been the inability to readily obtain consistent dyeability of fabrics made from polypropylene. Inasmuch as the polymerized propylene has no reactive sites to which dye molecules may be attached, ordinary dyeing techniques have not produced satisfactory fabrics. In general, a standard dyeing technique, such as vat dyeing, will produce only a surface coating of the dye, which is easily rubbed off. Various methods have been proposed for overcoming this problem, including the incorporation of various dye receptive materials in the polymer prior to extrusion of filaments, as well as various chemical treatments of the polypropylene after it has been formed, to produce reactive sites on the filaments which would allow the dye to adhere. None of these methods has been totally satisfactory, however, generally due to unevenness of the dye receptivity in various portions of the polypropylene fabric.

It is, therefore, an object of this invention to provide a process for dyeing of polypropylene. It is a further object of this invention to provide a method for improved dyeing of polypropylene filaments containing certain modifying agents. It is a further object of this invention to improve the dyeability of polypropylene compositions containing dye receptive modifiers. It is a still further object of this invention to provide a dyed polypropylene fabric.

These and other objects may be accomplished by my invention, which is that polypropylene containing certain modifiers is vat dyed in a reduced vat dyebath containing polyvinylpyrrolidone.

The process of my invention is applicable to polypropylene at any stage of textile manufacturing. The dyeing may be accomplished, for example, using filaments, fibers, tow, yarn, web, or fabric.

The polypropylene used in preparing the filaments from which the fibers, tow, yarn, web, or fabric is prepared the group consisting of the bis-amides and bis-urethanes represented by the formulas:

and

in which R is an alkyl group containing 5 to 25 carbon atoms, and R is an alkylene group containing 1 to 10 carbon atoms. The polypropylene contains at least 0.01 weight percent, preferably 0.2 to 20 weight percent, of at least one of the compounds represented by the above formulas, and can also contain at least 0.01 weight percent, preferably 0.2 to 20 weight percent, of an aliphatic amine containing 2 to 20 carbon atoms.

Examples of the bis-amides that can be used are: methylene bis-capramide methylene bis-stearamide, ethylene bis-caprylamide, ethylene bis-arachidamide, propylene, bis-caproamide, butylene bis-lauramide, pentylene bismyristamide, hexylene bis-palrnitamide, heptylene bisbehenamide, octylene bis-lignoceramide, nonylene biscerotamide, decylene bis-stearamide, methylene bis-lauramide, methylene bis-palmitamide, and the like.

Examples of the bis-urethanes that can be used are: methylene bis-P ntylurethane, ethylene bis-hexylurethane, propylene bis-heptylurethane, butylene bis-octylurethane, pentylene bis-nonylurethane, hexylene bis-undecylurethane, heptylene tridecylurethane, octylene bis-heptadecylurethane, nonylene bis-henicosylurethane, decylene bispentacosylurethane, methylene bis-pentadecylurethane, methylene bis-heptadecylurethane, and the like.

Examples of the aliphatic amines that can be used are: decylamine, 3,6-diethyloctylamine, laurylamine (dodecylamine), tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, ethylamine, butylamine, isooctylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, ethyleneimine, and the like.

The method of dyeing using the process of my invention is the well known vat dyeing. In this method, a dyestutf which is reducible to the sodium-leuco form is reduced in a bath with caustic and sodium hydrosulfit (Na S O Treatment with this reducing agent in the presence of an alkali forms the water soluble sodiumleuco form of dye. The fabric to be dyed is introduced to the reducing bath, allowing the aqueous solution of dye to penetrate the fibers of the fabric. The temperature of the dyebath will generally be around F., and the bath can contain wetting agents to aid in penetration of the dye throughout the fibers.

Following absorption of the dye solution into the fabric, the fabric is dried, leaving the soluble form of the dye dispersed throughout the fibers. The fabric is then subjected to chemical oxidation. The purpose of the oxidation is to convert the water soluble sodium-leuco form back to tl insoluble pigment, the form with which the desirable fastness properties of the vat dyes is associated.

Many dilferent chemicals are used as oxidizing agents; none is satisfactory for all vat dyes. Sodium perborate, sodium bichromate in acetic acid, hydrogen peroxide, sodium hypochlorite and sodium, ammonium, or potassium persulfate are the chemicals most commonly used.

The final step in the vat dyeing operation is that of soaping. The dyed and oxidized fibers are treated in a boiling soap solution. This operation will remove any dyestuff formed on the surface of the fibers, and will obtain the final shade and improve the light fastness of the dyed fabric.

Broadly, vat dyes are defined as those dyes which are insoluble in their oxidized form, but water soluble in their reduced form. Two representative classes of such vat dyestuffs are the well known indigoid and the anthraquinoid dyes. These and any other dyes suitable for the vat dyeing process can be used in practicing the process of my invention, and my invention is not to be construed as being limited to any specific class of dyestuffs.

In practicing the process of my invention, polyvinylpyrrolidone is dissolved in a reduced dyebath prior to introduction of the fabric. The concentration of the polyvinylpyrrolidone can be from 0.1 weight percent to 10 weight percent, and in the currently preferred embodiment is from 0.25 weight percent to 5 weight percent. The temperature of the dyeing operation is the same temperature that would be used were the polyvinylpyrrolidone not present, that is, 60 to 205 F. for most of the vat dyes. The length of contact of the fabric with the dye solution is not changed when polyvinylpyrrolidone is added to the dyebath, and generally will be in the range of from 0.5 hour to 3 hours depending upon the particular fabric being dyed, and the characteristics of the particular dyebath. It is thus seen that the process of my invention in no way changes normal dyeing operations.

The polyvinylpyrrolidone used in the process of my invention has the formula in which R is hydrogen or methyl; R is hydrogen, methyl, or ethyl; and n is a number representing the degree of polymerization. The total molecular weight of the polymer can vary from about 10,000 to about 500,000. In the practice of my invention, it is preferred to use a polyvinylpyrrolidone having a molecular weight of 30,000 to 50,000 obtained by polymerizing materials such as N-vinyl-Z- pyrrolidone, N-vinyl-S-methylpyrrolidone, N-vinyl-S-ethylpyrrolidone, N-vinyl-3,3-dimethylpyrrolidone, N-vinyl- 4-methylpyrrolidone, N-vinyl-4-ethylpyrrolidone, and the like.

EXAMPLE An aqueous dyebath was prepared by dissolving an excess of Ciba Blue 2B vat dye in an aqueous solution of 1 weight percent sodium hydrosulfite and 3 weight percent sodium hydroxide. This bath was used as the control bath. A duplicate bath was prepared, and 0.5 weight percent of polyvinylpyrrolidone (Antara-NPK30, M. W. 40,000) was added. Both baths were heated to 200 F. and small amounts of sodium hydrosulfite and sodium hydroxide were added as required to solubilize the dye. Samples of the fabric were dyed by immersion in the bath for 1% hours at 200 F. in a Gibbs Machine, which reciproca'tes samples continually in the dyebath. The samples were then oxidized with a weight percent sodium perborate solution for minutes at 200 F. to fix the dye. They were then soaped in soap solution for 30 minutes at 200 F., rinsed, dried, and evaluated.

Three different samples of material were dyed by the above process. Sample #1 was unmodified polypropylene yarn. Sample #2 was polypropylene yarn containing about 5 percent by weight laurylamine, and about 5 percent by weight methyl bis-stearamide. Sample #3 was polypropylene containing about 3 percent by weight polyvinylpyridine. The polypropylene used in preparing these samples was made with an organometal catalyst system and had a melt flow of 5. Evaluation of the samples was based on evenness of dye acceptance. Results of these runs are shown in the table below, with evenness of dyeing being expressed as good, fair, or poor.

Control bath PVP bath Sample 1 Fair Poor. Sample 2 do Good. Sample 3 do-. Poor.

Thus, it is shown that the process of my invention is applicable only to polypropylene containing certain additives as described above. Unmodified polypropylene is not improved in dyeability by the addition of polyvinylpyrrolidone to the dyebath. Moreover, polypropylene having a modifier such as polyvinylpyridine is not improved in dyeability by the addition of polyvinylpyrrolidone to the dyebath, but only polypropylene having additives of the classes described above are improved in dye receptivity by the addition of polyvinylpyrrolidone to the reduced dyebath.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, and the appended claims to the invention, the essence of which is that polypropylene containing certain additives is vat dyed in a dyebath containing polyvinylpyrrolidone.

I claim:

1. Process for vat dyeing polypropylene textile material containing 0.001 to 20 weight percent of a modifier selected from bis-amides, bis-urethanes, and combinations thereof comprising dyeing said polypropylene in a dye bath having dissolved therein 0.1 to 10 weight percent polyvinylpyrrolidone.

2. Process of claim 1 wherein said polypropylene additionally contains 0.01 to 20 weight percent of an aliphatic amine modifier.

3. Process of claim 1 wherein said polyvinylpyrrolidone is wherein R is hydrogen or methyl; R is hydrogen, methyl, or ethyl; and n is a number representing the degree of polymerization and having a value such that the molecular weight of the polymer is in the range 10,000 to 500,000.

4. Process of claim 1 wherein said dyeing is conducted at a temperature of 60 to 205 F.

5. Process of claim 1 wherein said polypropylene contains laurylamine and methylene bis-stearamide, and said dyeing takes place in a reduced bath containing about 0.5 weight percent of polyvinylpyrrolidone.

6. Process of claim 1 wherein said polyvinylpyrrolidone is a poly(N-vinyl-2-pyrrolidone) having a molecular weight of around 40,000.

7. The dyed polypropylene product formed by the process of claim 1.

References Cited UNITED STATES PATENTS 2,971,812 2/1961 Moran et al. 834 3,233,960 2/1966 Lonardo 834 3,241,905 3/1966 Olaj et al. 8-34- FOREIGN PATENTS 628,687 1963 Belgium.

NORMAN G. TORCHIN, Primary Examiner J. E. CALLAGHAN, Assistant Examiner US. Cl. X.R. 8-172, 180 

